Postulated beneﬁts include improvements in cerebral blood flow (CBF) impacting on neuronal functioning, memory and learning capabilities, as well as neuronal protection and regeneration which impacts on the prevention on memory and cognitive decline during brain ageing (1, 2). Such effects are especially seen with the consumption of citrus fruits, blueberries, grapes and their juices (3).

Two recent studies, published in the British Journal of Nutrition (4) and in Neurology (5), provide further evidence that there is a potential effect of regular consumption of 100% fruit juice on brain function.

In the first study (4), dietary data collected since 1986 from 27,842 male participants in the Health Professionals Follow-up Study were analysed alongside two self-reported and validated questionnaires. The questionnaires, completed four years apart, were designed to capture early, small signs of cognitive decline. The researchers specifically investigated consumption of total and speciﬁc fruits, vegetables, and juices in relation to future subjective cognitive function (SCF).

Results showed that the highest habitual intakes of total vegetables, total fruits, and pure fruit juices were signiﬁcantly associated with lower odds of moderate or poor SCF. The most significant finding concerned orange juice consumers. Compared with those who reported drinking orange juice less than once per month, men who drank orange juice daily were 47% less likely to show signs of poor SCF after four years, suggesting that regular consumption of orange juice during middle and older age may have a protective effect in later life SCF.

The second study (5), a single-blind cross-over trial, examined the protective role of components of 100% citrus juice. Twenty-four healthy young adults consumed 500 mL of either a high-ﬂavanone (70·5 mg) pure citrus juice (orange and grapefruit) or an energy-, and vitamin C- matched, zero-ﬂavanone control drink. Subjects underwent cognitive testing at baseline and 2 hours after drink consumption. The results showed that the high-ﬂavanone drink was associated with significantly improved performance on the Digit Symbol Substitution Test at 2 hours relative to baseline and the control drink. No effects were observed on any other behavioural cognitive tests.

Additionally, 16 more healthy young adults were included in a study of the effects of test drinks on CBF, using MRI, before and after consuming either the 100% juice or the control drink. The results showed that, after consuming the high-ﬂavanone drink, there was signiﬁcantly increased CBF, demonstrated by regional perfusion in the inferior and middle right frontal gyrus, compared with baseline and the control drink. In addition, the high-ﬂavanone drink was associated with signiﬁcantly improved performance in some, although not all, of the cognitive tests.

The researchers concluded that: “These results demonstrate that consumption of ﬂavanone-rich citrus juice in quantities commonly consumed can acutely enhance blood ﬂow to the brain in healthy, young adults. However, further studies are required to establish a direct causal link between increased CBF and enhanced behavioural outcomes following citrus juice ingestion”.

The evidence from this acute study, and others on flavonoid-rich juices (6), adds to the hypothesis that ﬂavonoid consumption can improve performance in some neuropsychological tests and deliver cognitive beneﬁts. This may occur in part as a consequence of enhanced blood ﬂow to speciﬁc regions of the brain in the immediate postprandial period. Furthermore, the cohort study suggests that these effects might have longer term implications for slowing the earliest signs of cognitive decline in older adults who consume 100% juice daily.

For more information, see:

(1) Spencer JPE (2010) Beyond antioxidants: the cellular and molecular interactions of ﬂavonoids and how these underpin their actions on the brain. Proc Nutr Soc 69, 244–260.